This invention pertains to a pinch valve that is accessible by means of a tapered cannula and is particularly suited for use in the fields of combinatorial and biological chemistry. The pinch valve maintains the controlled interior atmosphere of a vessel sealed with the pinch valve, yet still allows for addition or removal of material from the vessel.
It is often desirable to run chemical reactions at higher temperatures. Higher temperatures can increase the reaction rate of experiments performed under these conditions. However, experiments that involve higher temperatures and/or require the presence of volatile solvents present a number of difficulties which are not a concern when reactions are carried out at ambient temperature or with non-volatile solvents. In these high temperature experiments, if a component of the reaction mixture is to be added after the start of the reaction, or if an aliquot is to be removed before the reaction is complete, the vessel must be accessed, typically by a cannula. In accessing the vessel, quantities of the volatilized solvent may be lost to the ambient atmosphere and the sterility of the vessel may be compromised. The present invention solves this problem.
Currently, there is no commercially available valve to address this problem. Several valves have been developed to solve similar problems in surgical procedures, however, none of these are adaptable to the immediate problem. U.S. Pat. No. 4,917,668, e.g., discloses a valve for permanent venous cannulae. The ""668 valve is designed to be placed directly in the bloodstream, however, its plastic construction is not rigid and durable enough for chemical applications; nor is the seal likely to be tight enough to prevent the loss of volatilized material. Many experimentally useful solvents are corrosive to plastic and therefore, these materials cannot be used in the construction of such a valve. Other devices known in the art include those disclosed in U.S. Pat. No. 5,207,409 for use as an inline member of a tubing system; in U.S. Pat. No. 5,342,316 as a placement designed to permit cannula access although exclusively through a Luer syringe cone; or in U.S. Pat. No. 5,498,253 where a device designed to permit attachment of modified tubing to packaged medical solutions is disclosed. Other pinch valves, such as those disclosed in U.S. Pat. No. 4,044,989, have been developed which utilize a piston to compress the tubing and thereby prevent access to the interior of the vessel. The pistons pinch the tubing and are controlled either manually or electrically. These valves do not reseal automatically requiring either an operator-controlled electrical signal or manual operation of an attached handle. A final approach to solve this problem is disclosed in U.S. Pat. No. 4,944,736 where an adaptor that has an attached cap which maintains the sterility of the contents of the vessel, but is not polytetrafluoroethylene (PTFE)-coated is used. This device requires removal and replacement of the cap to gain access to the material in the sealed vessel, and is designed to fit over a septum-sealed vessel. None of these devices meet all of the requirements that the valve be hemically resistant, continually accessible by cannula, reusable or disposable at the operator""s discretion, and adaptable to a range of laboratory research applications.
Accordingly, there is a need in the industry for a valve that will meet all the above criteria. Methods other than pinch valves have been considered in addressing this problem, but without success. For example, septa of different compositions have been used to close and seal containers and vessels. Septum-based solutions suffer from the problem that the vessel""s seal is no longer intact following the initial cannula puncture. In the case of PTFE-coated elastomeric closures, punctures leave a jagged aperture that does not reseal effectively. As a result, volatiles may escape and high temperature experiments are not feasible. Rubber septa reseal more tightly but are susceptible to corrosive solvents and can release particulate matter into the reaction mixture upon being pierced, thereby contaminating it. In both cases, large diameter cannulae make the breach more pronounced. In the case of 96 well plates, a common platform for chemical and biological reactions, a proposed solution is to cover the plate with a sheet of PTFE-coated elastomer, however this solution also fails to solve the above problems.
Thus, the primary object of the instant invention is the sealing of a vessel using a means that permits access of a tapered cannula while still maintaining the controlled atmosphere of the vessel. A further objective of the invention is the application of the invention to a chemical, biological or clinical setting. A still further object is to allow for adaptation of the invention to robotic or automated systems.
There is disclosed a device for sealing vessels which still permits access by a tapered cannula. In particular, a device comprising a metal spring or other elastomeric material surrounding a length of polytetrafluoroethylene (PTFE) tubing, which is itself encased in PTFE shrink-sleeve or other structural support is provided.